Electrophotographic plate with silicon naphthalocyanine

ABSTRACT

An electrophotographic plate comprising an electroconductive support and a photoconductive layer containing a naphthalocyanine compound having siloxy groups bonded to the central metal silicon as a charge generating substance has high sensitivity to the longer wavelength light of about 800 nm without conducting a special treatment.

BACKGROUND OF THE INVENTION

This invention relates to an electrophotographic plate having highsensitivity for a long wavelength light of about 800 nm which is in adiode laser region.

Electrophotographic plates have been produced by forming a selenium (Se)film of about 50 μm thick on an electroconductive substrate made of, forexample, aluminum, by a vacuum deposition method. But the Se plate has aproblem in that it has sensitivity only upto a wavelength of near 500nm. On the other hand, there have been known electrophotographic platesproduced by forming a Se layer of about 50 μm on an electroconductivesubstrate, followed by the formation of a selenium-tellurium (Se-Te)alloy layer of several μm thick. Such electrophotographic plates canextend the spectral light-sensitivity to a longer wavelength side bymaking the Te content in the Se-Te alloy higher. But with an increase ofthe Te adding amount, the surface charge retention properties of suchelectrophotographic plates become worse and cannot be used practicallyas an electrophotographic plate: this is a serious problem.

It is also known so-called complex double layer type electrophotographicplates produced by forming a charge generation layer on an alumiumsubstrate by coating chlorocyan blue or squaraine derivative in about 1μm thickness, and forming a change transport layer thereon by coating apolyvinylcarbazole having high insulation resistance or a mixture of apyrazoline derivative and polycarbonate in 10-20 μm thickness. But suchelectrophotographic plates have practically no sensitivity to a lighthaving a wavelength of 700 nm or more. Further, it is also knownelectrophotographic plates improved in the defect of the complex doublelayer type mentioned above so as to have sensitivity in about 800 nmwhich is in the diode laser region. But many of them show the longerwavelength sensitivity by forming a thin film with about 1 μm filmthickness of a metal phthalocyanine having one or more metals of thegroup III or IV of the periodic table as center metals by a vacuumdeposition method, and immersing the resulting thin film in a shiftingagent solution or contacting the resulting thin film with a vapor of theshifting agent so as to shift the absorption of original about 700 nm toabout 800 nm. On the thus treated thin film, a charge transport layer isformed by coating a polyvinylcarbazole having high insulation resistanceor a mixture of a pyrazoline derivative or a hydrazone derivative and apolycarbonate resin or polyester resin in 10-20 μm thickness to producecomplex double layer type electrophotographic plates. But in this case,since the metal phthalocyanine thin film having the metals of the groupIII or IV of the periodic table as center metals used as a chargegeneration layer has no absorption in the diode laser region of about800 nm essentially, there is a serious problem in that suchelectrophotographic plates have no sensitivity or only low sensitivityto the light of about 800 nm (U.S. Pat. No. 4,426,434).

In laser beam printers using electrophotographic plates and laser beamsas a light source, the use of diode laser as the light source has beentried variously in recent years. In this case, since the wavelength ofthis light source is about 800 nm, it is strongly desired to produceelectrophotographic plates having high sensitivity to the longerwavelength light of about 800 nm.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an electrophotographicplate having high sensitivity to the longer wavelength light of about800 nm essentially without conducting special treatment.

This invention provides an electrophotographic plate comprising anelectroconductive support and a photoconductive layer containing anorganic photoconductive substance as a charge generating material formedon the support, said organic photoconductive substance being anaphthalocyanine compound represented by the formula: ##STR1## wherein Lis a group of the formula: R₁ R₂ R₃ Si--O--; R₁, R₂ and R₃ areindependently hydrogen, an alkyl group or an alkoxy group.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is absorption spectra of a naphthalocyanine having twotrihexylsiloxy groups bonded to the central metal silicon synthesized inSynthesis Example 1 (solid line), and a phthalocyanine similar to it(dotted line).

FIG. 2 is an absorption spectrum of a vapor deposited film ofnaphthalocyanine having two trihexylsiloxy groups bonded to the centralmetal silicon synthesized in Synthesis Example 1.

FIG. 3 is an NMR spectrum of bis(triethylsiloxy)siliconnaphthelocyanine.

FIG. 4 is a UV spectrum of bis(triethylsiloxy)silicon naphthalocyanine.

FIG. 5 is an NMR spectrum of bis(tri-n-butylailoxy)siliconnaphthalocyanine.

FIG. 6 is a UV spectrum of bis(tri-n-butylsiloxy)siliconnaphthalocyanine.

FIG. 7 is an NMR spectrum of bis(tri-n-propylsiloxy)siliconnaphthalocyanine.

FIG. 8 is a UV spectrum of bis(tri-n-propylsiloxy)siliconnaphthalocyanine.

FIG. 9 is a UV spectrum of bis(trimethylsiloxy)silicon naphthalocyanine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The naphthalocyanine compound of the formula: ##STR2## wherein L is agroup of the formula: R₁ R₂ R₃ Si--O--; R₁, R₂ and R₃ are independentlyhydrogen, an alkyl group preferably having 1 to 12 carbon atoms, or analkoxy group preferably having 1 to 12 carbon atoms, generates charge byirradiation of a light.

The naphthalocyanine compound of the formula (I) can be produced byreacting dihydroxy-silicon naphthalocyanine of the formula: ##STR3##with a compound of the formula:

    R.sub.1 R.sub.2 R.sub.3 SiX                                (III)

wherein R₁, R₂, and R₃ are as defined above; and X is a hydroxyl groupor a halogen with heating.

In this case, the reaction temperature is preferably from 150° to 200°C. Further, it is preferable to use an organic solvent such as tetralin,chlorobenzene, quinoline, 1-chloronaphthalene, 1,2,4-trimethylbenzene,1,2,3-trimethylbenzene, xylene, toluene, benzene, dichlorobenzene,β-picoline, etc. alone or as a mixture thereof. Further, when X is ahalogen in the compound of the formula (III), it is preferable to use acatalyst such as tri-n-butylamine, tri-n-propylamine, tri-n-hexylamine,pyridine, or the like base. The catalyst is preferably used in an amountof 0.1 to 1% by weight based on the weight of dihydroxysiliconnaphthalocyanine.

In the production of bis(triethylsiloxy)silicon naphthalocyanine, it isbetter to use triethylsilanol than to use triethylchlorosiliconconsidering the yield.

Separation and purification of the bis(trialkylsiloxy)siliconnaphthalocyanine from the reaction mixture can be carried out by amethod comprising concentrating the reaction mixture, drying it andrecrystallizing it, or a method wherein the reaction mixture is pouredinto a poor solvent for the above-mentioned naphthalocyanine such aswater, methanol, ethanol, propanol, or the like alcohol, a producedprecipitate is collected and subjected to recrystallization, or thelike.

The recrystallization can be carried out by using the above-mentionedaromatic solvent or halogen series solvent.

Dihydroxysilicon naphthalocyanine is a known compound and can beproduced, for example, by the method described in J. Am. Chem. Soc. Vol.106, pp 7404- (1984) and the route (A) as shown below: ##STR4##

That is, α,α,α',α'-tetrabromo-o-xylene [the formula (V)] in an amount of0.1 mol and fumaronitrile in an amount of 0.178 mol are reacted at 75°C. for 7 hours in the presence of 0.67 mol of sodium iodide in anhydrousN,N-dimethylformamide to yield 2,3-dicyanonaphthalene of the formula(VI). Subsequently, 57.3 mmol of the 2,3-dicyanonaphthalene is reactedwith ammonia in the presence of sodium methoxide in methanol withheating for 3 hours to yield 1,3-diiminobenzo(f)isoindoline of theformula (VII). Further, 30.6 mmol of the 1,3-diiminobenzo(f)isoindolinewas reacted with 47.1 mmol of silicon tetrachloride in anhydroustetralin and anhydrous tri-n-butyl-amine under reflux for about 3 hoursto give dichlorosilicon naphthalocyanine [SiNoX₂ (X═Cl)] which can berepresented by the formula (II) except that the two OHs are replaced bytwo Cl's. Then, this compound is treated with concentrated sulfuric acidand then concentrated ammonia water to give dihydroxysiliconnaphthalocyanine [SiNcX₂ (X═OH)] of the formula (II).

The dihydroxysilicon naphthalocyanine of the formula (II) is reactedwith a compound of the formula (III), for example, a chlorosilanecompound of the formula:

    R.sub.1 R.sub.2 R.sub.3 SiCl                               (III')

wherein R₁, R₂ and R₃ are as defined above, at 140° to 150° C. for 1.0to 3.0 hours, e.g. 1.5 hours to yield the naphthalocyanine compound ofthe formula (I) wherein the two siloxy groups of the formula: R₁ R₂ R₃Si--O-- are bonded to the central metal silicon.

Examples of the siloxy group of the formula: R₁ R₂ R₃ Si--O-- are adimethylsiloxy group, a trimethylsiloxy group, a dimethoxymethylsiloxygroup, a dimethylpropylsiloxy group, a t-butyldimethylsiloxy group, atriethylsiloxy group, a triethoxysiloxy group, a tripropylsiloxy group,a dimethyloctylsiloxy group, a tributylsiloxy group, a trihexylsiloxygroup, etc.

The electrophotographic plate of this invention is produced by forming aphotoconductive layer on an electroconductive support.

The photoconductive layer is a layer containing an organicphotoconductive substance, and can be in the form of a film of anorganic photoconductive substance, a film containing an organicphotoconductive substance and a binder, a complex type film comprising acharge generation layer and a charge transport layer, etc.

As the organic photoconductive substance, the naphthalocyanine of theformula (I) is used as an essential component. It is possible to co-useone or more conventional photoconductive substances. It is preferable touse the naphthalocyanine of the formula (I) alone or in combination withone or more organic pigments generating charge together with one or morecharge transport substances. In the above-mentioned charge generationlayer, the naphthalocyanine of the formula (I) and the organic pigmentsgenerating charge are contained, and in the charge transport layer, thecharge transport substances are contained.

As the organic pigment which is included in the charge generation layerfor charge generation, there can be used azoxybenzenes, disazos,trisazos, benzimidazoles, multi-ring quinones, indigoids, quinacridones,metallic or non-metallic phthalocyanines having various crystalstructures, perylenes, methines, etc., these pigments being known forcharge generation. These pigments can be used alone or as a mixturethereof. These pigments are, for example, disclosed in British Pat. Nos.1,370,197, 1,337,222, 1,337,224 and 1,402,967, U.S. Pat. Nos. 3,887,366,3,898,084, 3,824,099 and 4,028,102, Canadian Pat. No. 1,007,095, GermanOffenlegungsschrift No. 2,260,540, etc. It is also possible to use allorganic pigments which can generate charge carriers by illumination withlight other than those mentioned above.

A part of typical examples of the organic pigments are illustratedbelow, but needless to say, the organic pigments are not limitedthereto.

Examples of the phthalocyanine series pigments are copperphthalocyanine, metal free phthalocyanines, magnesium phthalocyanine,aluminum phthalocyanine, chromium phthalocyanine, copper-sulfatedphthalocyanine, etc. As to their crystal forms, α-form, β-form, γ-form,ε-form, χ-form, etc., may be used. Particularly, the use of τ, τ', η andη' type metal free phthalocyanines disclosed in U.S. Pat. No. 4,619,879,etc. is preferable.

As the charge transport substances, there can be used high polymericcompounds such as poly-N-vinylcarbazole, halogenatedpoly-N-vinylcarbazole, polyvinylpylene, polyvinylindoloquinoxaline,polyvinylbenzothiophene, polyvinylanthracene, polyvinylacridine,polyvinylpyrazoline, etc., low molecular-weight compounds such asfluorenone, fluorene, 2,7-dinitro-9-fluorenone,4H-indeno(1,2,6)thiophene-4-one, 3,7-dinitro-dibenzothiophene-5-oxide,1-bromopyrene, 2-phenylpyrene, carbazole, N-ethylcarbazole,3-phenylcarbazole, 3-(N-methyl-N-phenylhydrazone)methyl-9-ethylcarbazole, 2-phenylindole, 2-phenylnaphthalene,oxadiazole, 2,5-bis(4-diethylaminophenyl) -1,3,4-oxadiazole,1-phenyl-3-(4-diethylaminostyryl)-5-(4-diaminostyryl)-5-(4-diethyl-aminophenyl)pyrazoline,1-phenyl-3-(p-diethylaminophenyl)-pyrazoline,p-(dimethylamino)-stilbene,2-(4-dipropyl-aminophenyl)-4-(4-dimethylaminophenyl)-5-(2-chlorophenyl)-1,3-oxazole,2-(4-dimethylaminophenyl)-4-(4-dimethyl-aminophenyl)-5-(2-fluorophenyl)-1,3-oxazole,2-(4-diethylaminophenyl)-4-(4-dimethylaminophenyl)-5-(2-fluorophenyl)-1,3-oxazole,2-(4-dipropylaminophenyl)-4-(4-dimethylaminophenyl)-5-(2-fluorophenyl)-1,3-oxazole,imidazole, chrysene, tetraphene, acridine, triphenylamine, andderivatives of these compounds.

When the naphthalocyanine compound of the formula (I) with or withoutthe organic pigments which generate charge is used in admixture with thecharge transport substances, it is preferable to mix the former/thelatter in a weight ratio of 10/1 to 2/1. When a high polymeric compoundis used as the charge transport substance, the use of a binder is notalways necessary. But in such a case or a low molecular-weight compoundis used as the charge transport substance, it is preferable to use thebinder in an amount of 30% by weight or more. Further, even if thecharge transport substance is not used, the binder may be used in thesame amount as mentioned above. When the binder is used, there can beused one or more additives such as plasticizers, flowability impartingagents, pin hole inhibiting agents, etc., depending on purposes.

When a complex type photoconductive layer comprising a charge generationlayer and a charge transport layer is formed, the naphthalocyaninecompound of the formula (I) with or without an organic pigment which cangenerates charge is contained in the charge generation layer which maycontain the binder in an amount of 500% by weight or less based on theweight of the organic pigment, or contain the additives in an amount of5% by weight or less based on the weight of the naphthalocyaninecompound of the formula (I) or a total amount of the naphthalocyaninecompound of the formula (I) and the organic pigment. The chargetransport substance is contained in the charge transport layer which maycontain the binder in an amount of 500% by weight or less based on theweight of the charge transport substance. When the low molecular-weightcompound is used as the charge transport substance, it is preferable tocontain the binder in an amount of 50% by weight or more based on theweight of the low molecular-weight compound. The charge transport layermay contain the above-mentioned additive in an amount of 5% by weight orless based on the weight of the charge transport substance.

As the binder which can be used in all the cases mentioned above, therecan be used silicone resins, polyamide resins, polyurethane resins,polyester resins, epoxy resins, polyketone resins, polycarbonate resins,polyacrylic resins, polystyrene resins, styrene-butadiene copolymers,polymethyl methacrylate resins, polyvinyl chlorides, ethylene-vinylacetate copolymers, vinyl chloride-vinyl acetate copolymers,polyacrylamide resins, polyvinylcarbazole, polyvinylpyrazoline,polyvinylpyrene, etc. It is also possible to use one or morethermosetting resins and photo-curable resins which are crosslinked byheat and/or light.

In any cases, there is no particular limitation to the resins, so longas they can form insulating films under normal conditions or can formfilms by curing with heat and/or light.

As the plasticizers, there can be used conventional ones such ashalogenated paraffins, dimethyl naphthalene, dibutyl phthalate, etc. Asthe flowability imparting agents, there can be used conventional onessuch as Modaflow (a trade name mfd. by Monsanto Chemical Co.), Akulonal4F (a trade name mfd. by BASF AG.), etc. As the pin hole inhibitingagents, there can be used conventional ones such as benzoine, dimethylphthalate, etc. These additives can be used depending on purposes inamounts suitable for purposes.

As the electroconductive support for forming an electroconductive layer,there can be used paper or plastic films subjected to theelectroconductivity treatment, plastic films clad with a metal foil suchas aluminum, metal plates, and the like.

The electrophotographic plate of this invention comprises anelectroconductive support and a photoconductive layer formed thereon.The thickness of the photoconductive layer is preferably 5 to 50 μm.When the complex type comprising the charge generation layer and thecharge transport layer is used as the photoconductive layer, thethickness of the charge generation layer is preferably 0.001 to 10 μm,more preferably 0.2 to 5 μm. When the thickness is less than 0.001 μm,it is difficult to form the charge generation layer uniformly, whereaswhen the thickness is more than 10 μm, there is a tendency to lowerelectrophotographic properties. The thickness of the charge transportlayer is preferably 5 to 50 μm, more preferably 8 to 20 μm. When thethickness is less than 5 μm, the initial potential is lowered, whereaswhen the thickness is more than 50 μm, there is a tendency to lower thesensitivity.

The photoconductive layer can be formed on the electroconductive supportby a vapor deposition method wherein an organic photoconductivesubstance is vapor deposited on the electroconductive support, or by acoating method wherein an organic photoconductive substance and othercomponents depending on purposes are dissolved or dispersed uniformly ina solvent and coated on the electroconductive support, followed bydrying. As the solvent, there can be used ketones such as acetone,methyl ethyl ketone, etc.; ethers such as tetrahydrofuran, etc.;aromatic compounds such as toluene, xylenes, etc.; halogenatedhydrocarbons such as methylene chloride, carbon tetrachloride, etc.;alcohols such as methanol, ethanol, propanol, etc. As the coatingmethod, there can be used conventional ones such as a spin coatingmethod, a dip coating method, etc.

In the case of forming the charge generation layer and the chargetransport layer, the above-mentioned methods can also be employed. Insuch a case, either the charge generation layer or the charge transportlayer may be formed as an upper layer, or one charge generation layermay be sandwiched between two charge transport layers.

When the naphthalocyanine compound of the formula (I) is vacuumdeposited, it is preferable to heat the naphthalocyanine compound in ahigh vacuum of 10⁻⁵ to 10⁻⁶ mm Hg. In the case of coating thenaphthalocyanine compound by a spin coating method, it is preferable touse a coating solution obtained by dissolving the naphthalocyaninecompound of the formula (I) in a halogenated solvent such as chloroformor an aprotic solvent such as toluene and to spin coat at a number ofrevolutions of 3000 to 7000 rpm. In the case of coating thenaphthalocyanine compound by a dipping method, it is preferable to dipthe electroconductive support in a coating solution obtained bydispersing the naphthalocyanine compound of the formula (I) in a polarsolvent such as methanol, dimethylformamide, etc. by using a ball mill,ultrasonic wave, or the like.

If necessary, a protective layer may be formed in the same manner asdescribed above for coating the photoconductive layer and drying it.

The electrophotographic plate of this invention may further contain athin adhesive layer or barrier layer immediately on theelectroconductive support, or a protective layer on the surface thereof.

This invention is explained in detail by way of the following SynthesisExamples for synthesizing the naphthalocyanine compounds of the formula(I) and Examples, in which all parts and percents are by weight unlessotherwise specified.

SYNTHESIS EXAMPLE 1 (1) Synthesis of 2,3-dicyanonaphthalene

To 0.1 mole of tetrabromoxylene, 0.17 mole of fumaronitrile, 0.66 moleof sodium iodide and 400 ml of anhydrous dimethylformamide were addedand heated with stirring at 70° to 80° C. for 7 hours. The reactionsolution was added to 800 g of ice water. To the deposited precipitate,about 15 g of sodium hydrogen sulfite was added and allowed to standovernight. After filtration by suction and drying, white2,3-dicyane-naphthalene was obtained by recrystallization fromchloroform/ethanol in yield of 80%.

(2) Synthesis of 1,3-diiminobenz(f)isoindoline

In 2.5 moles of 2,3-dicyanonaphthalene, 0.075 mole of sodium methoxideand 1 liter of methanol, an ammonia gas was flowed with a suitable flowrate for 40 minutes. Then, the reaction solution was refluxed withheating while flowing the ammonia gas for 4 hours. After cooling, theproduct was filtered, and recrystallized from a mixed solvent ofmethanol/ether to yield yellow 1,3-diiminobenz (f) isoindoline in 66%yield.

(3) Synthesis of dichlorosilicon naphthalocyanine

1,3-Diiminobenz (f) isoindoline in an amount of 3 millimoles, 4.8millimoles of silicon tetrachloride, 2 ml of dried tri-n-butylamine and4 ml of dried tetralin were refluxed with heating for about 2.5 hours.After cooling, 3 ml of methanol was added to the reaction solution, andallowed to stand. After filtering by suction and washing with methanolsufficiently, there was obtained dark green dichlorosiliconnaphthalocyanine in 24% yield.

(4) Synthesis of dihydroxysilicon naphthalocyanine

To 0.71 millimole of dichlorosilicon naphthalocyanine, 20 ml ofconcentrated sulfuric acid was added and stirred at room temperature for2 hours, followed by addition of 60 g of ice to the reaction solution.After filtering by suction and drying, the precipitate was placed in 60ml of 25% ammonia water and refluxed with heating for 1 hour to givedihydroxysilicon naphthalocyanine quantitatively.

(5) Synthesis of bis(trihexylsiloxy)silicon naphthalocyanine

To 0.8 millimole of dihydroxysilicon naphthalocyanine, 8 millimoles oftrihexylsilyl chloride and 70 ml of β-picoline were added and refluxedwith heating for 1.5 hours. After filtering, the filtrate was added to amixed solution of water/ethanol to deposit a precipitate. Afterfiltering the precipitate, it was recrystallized from n-hexane to give anaphthalocyanine compound in 50% yield.

SYNTHESIS EXAMPLE 2

Bis(dimethylpropylsiloxy)silicon naphthalocyanine was synthesized in thesame manner as described in Synthesis Example 1 except for usingdimethylpropylsilyl chloride in place of trihexylsilyl chloride in thestep (5).

SYNTHESIS EXAMPLE 3

Bis(triethylsiloxy)silicon naphthalocyanine was synthesized in the samemanner as described in Synthesis Example 1 except for usingtriethylsilyl chloride in place of trihexylsilyl chloride in the step(5).

SYNTHESIS EXAMPLE 4

Bis(tripropylsiloxy)silicon naphthalocyanine was synthesized in the samemanner as described in Synthesis Example 1 except for usingtripropylsilyl chloride in place of trihexylsilyl chloride in the step(5).

SYNTHESIS EXAMPLE 5

Bis(tributylsiloxy)silicon naphthalocyanine was synthesized in the samemanner as described in Synthesis Example 1 except for usingtributylsilyl chloride in place of trihexylsilyl chloride in the step(5).

SYNTHESIS EXAMPLE 6

Bis(dimethoxymethylsiloxy)silicon naphthalocyanine was synthesized inthe same manner as described in Synthesis Example 1 except for usingdimethoxymethylsilyl chloride in place of trihexylsilyl chloride in thestep (5).

SYNTHESIS EXAMPLE 7

Bis(triethoxysiloxy)silicon naphthalocyanine was synthesized in the samemanner as described in Synthesis Example 1 except for usingtriethoxysilyl chloride in place of trihexylsilyl chloride in the step(5).

EXAMPLE 1

Bis(trihexylsiloxy)silicon naphthalocyanine obtained in SynthesisExample 1 and having two trihexylsiloxy groups as L in the formula (I)was subjected to vacuum deposition in a vacuum of 2×10⁻⁵ mm Hg by aheating method to form a charge generation layer of 400 nm thick on analuminum vapor deposition substrate.

A coating solution obtained by dissolving 5 g of1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline and10 g of polycarbonate resin in 85 g of 1:1 mixed solvent of methylenechloride and 1,1,2-trichloroethane was coated on the charge generationlayer formed on the substrate by a dip coating method and dried at 120°C. for 30 minutes to form a charge transport layer of 15 μm thick.

Using an electrostatic charging analyzer (mfd. by Kawaguchi ElectricWorks Co., Ltd.), the resulting electrophotographic plate was chargednegatively by corona discharge at 5 kV. Then, by irradiating a lightobtained by using a halogen lamp as an outer light source and changingto a monochromatic light by using a monochrometer (mfd. by RITSUOYOKOGAKU Co., Ltd.), the light decay of the surface potential of theelectrophotographic plate was measured.

As a result, when a monochromatic light of 800 nm in the near infraredregion was used, the half decay exposure amount (the product of a timerequired for making the potential retention rate 1/2 by the lightintensity) was 20 mJ/m².

EXAMPLES 2 TO 5

Each charge generation layer was formed by vacuum deposition of thenaphthalocyanine compounds obtained in Synthesis Examples 2 to 5 havingtwo dimethylpropylsiloxy groups, triethylsiloxy groups, tripropylsiloxygroups, and tributylsiloxy groups, respectively.

A coating solution obtained by dissolving 5 g of1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline and10 g of polycarbonate resin in 85 g of 1:1 mixed solvent of methylenechloride and 1,1,2-trichloroethane was dip coated on the chargegeneration layer formed on the substrate and dried at 120° C. for 30minutes to form a charge transport layer of 15 μm thick.

The thus produced electrophotographic plates were subjected to the sametest as in Example 1 to measure the half decay exposure amount by usinga monochromatic light of 800 nm in the near infrared region. The resultsare shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Example                  Half decay exposure                                  No.       L in the formula (I)                                                                         amount (mJ/m.sup.2)                                  ______________________________________                                        2         Dimethylpropylsiloxy                                                                         25                                                   3         Triethylsiloxy  8                                                   4         Tripropylsiloxy                                                                              10                                                   5         Tributylsiloxy 17                                                   ______________________________________                                    

EXAMPLES 6 TO 10

Each charge generation layer was formed by vacuum deposition of thenaphthalocyanine compounds obtained in Synthesis Examples 1 to 5 in thesame manner as described in Examples 1 to 5.

A coating solution obtained by dissolving 5 g ofp-diethylaminobenzaldehyde-diphenylhydrazone and 10 g of polycarbonateresin in 85 g of 1:1 mixed solvent of methylene chloride and1,1,2-trichloroethane was dip coated on the charge generation layerformed on the substrate and dried at 120° C. for 30 minutes to form acharge transport layer of 15 μm thick.

The thus produced electrophotographic plates were subjected to the sametest as in Example 1 to measure the half decay exposure amount by usinga monochromatic light of 800 nm in the near infrared region. The resultsare shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Example                  Half decay exposure                                  No.       L in the formula (I)                                                                         amount (mJ/m.sup.2)                                  ______________________________________                                        6         Trihexylsiloxy 22                                                   7         Dimethylpropylsiloxy                                                                         28                                                   8         Triethylsiloxy 10                                                   9         Tripropylsiloxy                                                                              12                                                   10        Tributylsiloxy 20                                                   ______________________________________                                    

EXAMPLES 11 TO 17

A mixed solution of 2.5 g of a naphthalocyanine compound as listed inTable 3, 5.0 g of a silicone resin (XR-255, a trade name mfd. byShin-etsu Chemical Industry Co., Ltd.) (solid content 50%), and 92.5 gof methyl ethyl ketone was kneaded for 8 hours by using a ball mill (apot mill having a diameter of about 10 cm mfd. by NIPPON KAGAKU TOGYOCo., Ltd.). The resulting pigment dispersion was coated on an aluminumplate (an electroconductive support of 100 mm×70 mm) using an applicatorand dried at 90° C. for 13 minutes to form a charge generation layer of1 μm thick.

A coating solution obtained by dissolving 5 g of1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl) pyrazolineand 10 g of polycarbonate resin in 85 g of 1:1 mixed solvent ofmethylene chloride and 1,1,2-trichloroethane was dip coated on thecharge generation layer on the substrate and dried at 120° C. for 30minutes to form a charge transport layer of 15 μm thick.

The thus produced electrophotographic plates were subjected to the sametest as in Example 1 to measure the half decay exposure amount by usinga monochromatic light of 800 nm in the near infrared region. The resultsare shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        Example                  Half decay exposure                                  No.      L in the formula (I)                                                                          amount (mJ/m.sup.2)                                  ______________________________________                                        11       Trihexylsiloxy  35                                                   12       Dimethylpropylsiloxy                                                                          40                                                   13       Triethylsiloxy  18                                                   14       Tripropylsiloxy 20                                                   15       Tributylsiloxy  28                                                   16       Dimethoxymethylsiloxy                                                                         25                                                   17       Triethoxysiloxy 28                                                   ______________________________________                                    

COMPARATIVE EXAMPLE 1

An electrophotographic plate was produced in the same manner asdescribed in Example 1 except for using a phthalocyanine compound of theformula: ##STR5## wherein L is (C₆ H₁₃)₃ Si--O--, in place of thebis(trihexylsiloxy)silicon naphthalocyanine. The half decay exposureamount for the monochromatic light of 800 nm measured under the sameconditions as in Example 1 was 3000 mJ/m², which value means that thesensitivity is remarkably worse compared with Example 1.

COMPARATIVE EXAMPLE 2

An electrophotographic plate was produced in the same manner asdescribed in Comparative Example 1 except for usingp-diethylaminobenzaldehyde-diphenylhydrazone as a charge transportsubstance in place of1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline.The half decay exposure amount of the electrophotographic plate usingthe monochromatic light of 600 nm in the near infrared region measuredin the same manner as described in Example 1 was 3200 mJ/m².

REFERENCE EXAMPLE

Each solution was prepared by dissolving a phthalocyanine wherein twotrihexylsiloxy groups were bonded to the central metal silicon or anaphthalocyanine compound wherein two trihexylsiloxy groups were bondedto the central metal silicon (the naphthalocyanine compound synthesizedin Synthesis Example 1) in chloroform to measure an absorption spectrum.The results are shown in FIG. 1.

As is clear from FIG. 1, the phthalocyanine (the dotted line) showsabsorptions only in the region of 700 nm or less, whereas thenaphthalocyanine (the solid line) shows an absorption at near 800 nm.

FIG. 2 shows an absorption spectrum of a vacuum deposited film of theabove-mentioned naphthalocyanine. In this case, the absorption is shownat 800 nm.

As mentioned above, the electrophotographic plate of this inventionshows a large absorption at near 800 nm and has properties of showinghigh sensitivity for the longer wavelength region. Thus, when it is usedin a diode laser beam printer, excellent effects are exhibited. Further,the electrophotographic plate of this invention can be used not only forthe diode laser beam printer as mentioned above but also for FAX(facsimile telegraphy) or a printer using LED as a light source, andother light recording devices using a diode laser as a light source.

EXAMPLE 18

To a suspension of 35 ml of quinoline containing 774 mg (1 mmol) ofdihydroxynaphthalocyanine, 3.5 ml (23 mmol) of triethylsilanol was addedand refluxed for about 3 hours. After cooling, the reaction mixture waspoured into 200 ml of ethanol/water (1/1), stirred well and allowed tostand overnight. A deposited precipitate was filtered and washed withmethanol. A soluble portion of the precipitate was dissolved with about600 ml of hot chloroform and the resulting chloroform solution wasconcentrated to about 50 ml. After cooling the concentrated chloroformsolution, deposited crystals were filtered and washed with chloroform.The obtained crystals were recrystallized from chloroform to give 360 mgof dark green crystals in 36% yield. The dark green crystals wereidentified as bis(triethylsiloxy)silicon naphthalocylanine [L is--O--Si--(--C₂ H₅)₃ in the formula (I)] by the following analyticalresults.

(1) Melting point: >300° C.

(2) Elementary analysis:

    ______________________________________                                               C (%)       H (%)   N (%)                                              ______________________________________                                        Calcd.   71.82         5.42    11.17                                          Found    70.45         5.34    10.92                                          ______________________________________                                    

(3) NMR values (CDCl₃ solvent, FIG. 3) δ values 10.13 (8H, s) 8.68 (8H,dd, J=6.10, 3.05 Hz) 7.93 (8H, dd, J=6.10, 3.05 Hz) -1.02 (12H, t,J=7.93 Hz) -2.07 (18H, q, J=7.93 Hz)

(4) UV spectrum (CHCl₃ solution): FIG. 4

EXAMPLE 19

To 420 ml of a suspension of anhydrous β-picoline containing 3 g (3.9mmol) of dihydroxysilicon naphthalocyanine, 12 ml (50.4 mmol) ofanhydrous tri-n-butylamine and then 13.2 ml (49.2 mmol) oftri-n-butylchlorosilane were added in a nitrogen atmosphere and refluxedfor about 2 hours. After cooling, the resulting mixture was poured into600 ml of ethanol/water (1/1), stirred well and allowed to standovernight. A deposited precipitate was filtered and washed with water. Asoluble portion of the precipitate was dissolved with about 600 ml ofhot chloroform and the chloroform solution was dried over anhydroussodium sulfate, followed by concentration to about 50 ml. After coolingthe concentrated chloroform solution, deposited crystals were filteredand washed with chloroform. The mother liquid was concentrated andeluted by using benzene as a developing solvent by means of aluminacolumn chromatography. Then the green benzene solution was concentratedand added with hexane to deposit crystals, which were filtered andwashed with hexane sufficiently. All the obtained crude crystals wererecrystallized from chloroform to give about 2 g (44% yield) of darkgreen crystals. The dark green crystals were identified asbis(tri-n-butylsiloxy)silicon naphthalocyanine by the followinganalytical results.

(1) Melting point: >300° C.

(2) Elementary analysis:

    ______________________________________                                               C (%)       H (%)   N (%)                                              ______________________________________                                        Calcd.   73.81         6.71    9.50                                           Found    73.71         6.73    9.40                                           ______________________________________                                    

(3) NMR values (CDCl₃, FIG. 5) δ values 10.11 (8H, s) 8.67 (8H, dd,J=6.10, 3.35 Hz) 7.92 (8H, dd, J=6.10, 3.35 Hz) -0.1 to 0.1 (30H, m)-0.97 (12H, quintet, J=7.32 Hz) -2.07 (12H, t, J=7.32 Hz)

(4) UV spectrum (CHCl₃ solution): FIG. 6

EXAMPLE 20

To 420 ml of a suspension of anhydrous β-picoline containing 3 g (3.9mmol) of dihydroxysilicon naphthalocyanine, 12 ml (50.4 mmol) ofanhydrous tri-n-butylamine and then 10.8 ml (49.2 mmol) oftri-n-propylchlorosilane were added and refluxed for about 2 hours.After cooling, the reaction mixture was treated in the same manner asdescribed in Example 19 and the recrystallization was carried out usingchloroform. As a result, 1.45 g (34% yield) of dark green crystals wereobtained. The dark green crystals were identified asbis(tri-n-propylsilolxy)-silicon naphthalocyanine by the followinganalytical results.

(1) Melting point: >300° C.

(2) Elementary analysis:

    ______________________________________                                               C (%)       H (%)   N (%)                                              ______________________________________                                        Calcd.   72.89         6.12    10.30                                          Found    72.70         6.13    10.28                                          ______________________________________                                    

(3) NMR values (CDCl, FIG. 7) values 10.03 (8H, s) 8.68 (8H, dd, J=6.10,3.03 Hz) 7.93 (8H, dd, J=6.10, 3.03 Hz) -0.28 (18H, t, J=7.32 Hz) -0.85(12H, sextet, J=7.32 Hz) -2.06 (12H, t, J=7.32 Hz)

(4) UV spectrum (CHCl₃ solution): FIG. 8

EXAMPLE 21

To 140 ml of a suspension of anhydrous β-picoline containing 1 g (1.3mmol) of dihydroxysilicon naphthalocyanine, 4 ml (16.8 mmol) ofanhydrous tri-n-butylamine and then 2.1 ml (16.4 mmol) oftrimethylchlorosilane were added and refluxed for about 2 hours. Aftercooling, the reaction mixture was treated in the same manner asdescribed in Example 19 to give dark green crystals ofbis(trimethylsiloxy)silicon naphthalocyanine. FIG. 9 shows a UV spectrumof this compound (CHCl₃ solution).

What is claimed is:
 1. An electrophotographic plate comprising an electroconductive support and a photoconductive layer containing an organic photoconductive substance as a charge generating material formed on the substrate, said organic photoconductive substance being a naphthalocyanine compound represented by the formula: ##STR6## where L is a group of the formula: R₁ R₂ R₃ Si--O--; R₁, R₂ and R₃ are independently hydrogen, an alkyl group or an alkoxy group.
 2. An electrophotographic plate according to claim 1, wherein the photoconductive layer is a complex type comprising a charge generation layer containing the naphthalocyanine compound of the formula (I) and a charge transport layer.
 3. An electrophotographic plate according to claim 1, wherein the napthalocyanine compound is bis(trihexylsiloxy)silicon napthalocyanine, bis(dimethylpropylsiloxy)silicon naphthalocyanine, bis(triethylsiloxy)silicon naphthalocyanine, bis(tripropylsiloxy)silicon naphthalocyanine, bis(tributylsiloxy)silicon naphthalocyanine, bis(dimethoxymethylsiloxy)silicon naphthalocyanine, or bis(triethoxysiloxy)silicon naphthalocyanine.
 4. An electrophotographic plate according to claim 1, wherein the photoconductive layer comprises a charge generating substance and a charge transport substance.
 5. An electrophotographic plate according to claim 1, wherein the photoconductive layer is a film containing the naphthalocyanine compound of the formula (I) and a binder.
 6. An electrophotographic plate according to claim 2, wherein the naphthalocyanine compound in bis(trihexylsiloxy)silicon naphthalocyanine, bis(dimethylpropylsiloxy)silicon napththalocyanine, bis(triethylsiloxy)silicon naphthalocyanine, bis(tripropylsiloxy)silicon naphthalocyanine, bis(tributylsiloxy)silicon naphthalocyanine, bis(dimethoxymethylsiloxy)silicon naphthalocyanine, or bis(triethyxysiloxy)silicon naphthalocyanine. 